ASV users: the everything ASV thread.

[JohnBFisher]

...

Bons wrote: So, am I correct in thinking that if I move the Ti up to 3 it might help?

I defer to John's knowledge on this issue...

But as a general rule, and especially when you're unsure of what you're doing, take "baby steps" Not a radical jump from 1 second to 3 seconds. I believe T settings go down to tenths of a second increments. ...

Don't disagree with you ... and my knowledge is only from reading the manual and online websites. My ASV did not have Ti set. It was left at the default, which allows the BPM (breaths per minute) to determine the Ti (and if there were one, the Te) setting. But your point is well taken that a jump to 2 from 1 would be a big initial step.

[Bons]

Just tried to reset my Ti and the ASV will only allow me to up it to 2 - after that it resets to .5 if I continue to hit the up key..... But I'll try it on 3 tonight and see what happens. I'd upped it to 1.5 last night.

I REALLY have to find a doctor who actually knows something about these machines. It's also been a year, and unfortunately I gained a good bit of weight from my "menopausal muffin" so my insurance company might be willing to spring for another sleep study to actually have a decent titration for this thing (and maybe finally do something about my 175+ PLM's while we're at it.....).

Seems to me like all of these settings just fight with each other.... if bpm doesn't mesh with the Ti and the rise rate, what prevails? No wonder I can't get the hang of this thing.

[ameriken]

Just tried to reset my Ti and the ASV will only allow me to up it to 2 - after that it resets to .5 if I continue to hit the up key..... But I'll try it on 3 tonight and see what happens. I'd upped it to 1.5 last night.

I REALLY have to find a doctor who actually knows something about these machines. It's also been a year, and unfortunately I gained a good bit of weight from my "menopausal muffin" so my insurance company might be willing to spring for another sleep study to actually have a decent titration for this thing (and maybe finally do something about my 175+ PLM's while we're at it.....).

Seems to me like all of these settings just fight with each other.... if bpm doesn't mesh with the Ti and the rise rate, what prevails? No wonder I can't get the hang of this thing.

Bons, I'm curious why or how it came about that you took your machine off auto and set your own breath rate? What was the rationale? I've tried to do that with no success in trying to achieve the end results of better sleep, so I leave it on auto. Thanks!

[jamiswolf]

Bons wrote: Just tried to reset my Ti and the ASV will only allow me to up it to 2 - after that it resets to .5 if I continue to hit the up key..... But I'll try it on 3 tonight and see what happens. I'd upped it to 1.5 last night.

I'm assuming you mean 2 since that's the max your machine will go. Take a breath...a somewhat slow breath like you might do while sleeping. A 2 second breath is pretty long. And exhalation is usually even slower. Go back and read some old posts on this issue. Use search. Both John and Ameriken are saying you should use the auto T setting. They use these machines and know about them.

Ameriken, I seem to recall that this was the setting on her machine when she got it...if I'm not mistaken.

And searching for a Doctor that understands your machine may be futile. Your best bet might be the Respiratory Therapist at your DME's office. My Doc doesn't even understand my apap machine.
Jamis

[Bons]

When I'm awake I breathe at 8 bpm. It's normal for me. Sometimes I can pause for up to 15 seconds between finishing an exhalation and drawing my next breath. ASV's don't seem to like that very much- it thinks I'm having a CA. It's really obvious when you look at a print out from my ASV when I'm awake and asleep because my breath rate when asleep is much faster- about 16. Showed that to my sleep doctor, and he was amazed.

So if I set the parameters for when I'm awake, the ASV doesn't drive me nuts when I'm awake, and then adapts to my sleep rates. I think. Since I tweaked the bpm and rise rate my AHI has dropped from >5 to around 2.

I don't know how to set the TI on auto. Good at theology, lousy at anything technical. The machine lets me set it between .5 and 3 - there doesn't seem to be an auto setting like there is for the bpm.

When the machine was prescribed for me the rise rate was 2, the bpm was 12 and the Ti was 1. My RT called Respironics for me because she had no idea what the rise rate did, and they said that my breathing rate while awake is too slow for the ASV because it wants is designed with the expectation that people breathe at 10bpm or more, and told her I might want to set the rise rate at 6. I never asked her about the Ti. I set the bpm down to see what would happen and keep it slightly below what I usually breathe at while awake in attempt to deal with the IP/EP changing mid inhalation or exhalation for me.

[ameriken]

Thanks Bons, that's something I'm going to look into. My AHI's have been high and perhaps you're on to something.

On my sleep study report, the Dr said if I wasn't getting good results on auto, that they may go with a "different backup rate". However, I'm in the VA health care system and getting to see this doctor has been blockaded and I'm seeing a less than satisfactory doc.

I'm going to try again to see her, one of the RT's at the VA said she is the best sleep doc in Denver. Thanks for posting.

[sickwithapnea17]

I was wondering if bipap st isn't really working for me- I feel uncomfortable on the high setting 18/14 then should I get another sleep study? should I try to change to a different setting? the clear airway apneas seem to go away on the higher 18/14 and are higher at lower settings and I get 97% O2 on 18/14.

[ameriken]

I was wondering if bipap st isn't really working for me- I feel uncomfortable on the high setting 18/14 then should I get another sleep study? should I try to change to a different setting? the clear airway apneas seem to go away on the higher 18/14 and are higher at lower settings and I get 97% O2 on 18/14.

DId you see Johns response on the prior page? I think it's good advice: viewtopic.php?f=1&t=65791&st=0&sk=t&sd= ... 10#p644909

[jamiswolf]

Hi Guys,
Please allow me to run something by you. These are a general question and I don't necessarily mean it to apply to a specific machine. And also, I want to keep it simple...basic shit about how ST and SV machines work. I know they're different but they do have common features.

Let's assume that we're talking about complex apnea. Someone who has both obstructive events and central events. That's mostly the population these machines are used for, correct?

So obstructive events are primarily prevented through the use of increased pressure in the airway to "splint" the airway open. With a BiPap ST for example, the BiPap pressures are primarily set to deal with obstructive events.

THEN...

If a central apnea occurs, the machines respond by increasing airway pressure in an attempt to trigger a patient breath or to breathe for him (as the case may be).

The first question is this: Is there a pressure relationship between the BiPap settings and the spikes triggered by central apneas? Are these machines sort of two machines in one?

In other words, could you have your BiPap pressures fairly low and yet the Central spikes will still go up possible as high as 25cmH2O or more?

What determines how high those spikes will go?

And is it the spikes that make it most difficult to get use to these machines?

Remember, please keep it simple. I'm asking these question as a proxy.
Jamis

[moresleep]

Hi Guys,
...
The first question is this: Is there a pressure relationship between the BiPap settings and the spikes triggered by central apneas? Are these machines sort of two machines in one?

In other words, could you have your BiPap pressures fairly low and yet the Central spikes will still go up possible as high as 25cmH2O or more?

What determines how high those spikes will go?

And is it the spikes that make it most difficult to get use to these machines?

Remember, please keep it simple. I'm asking these question as a proxy.
Jamis

With the Respironics ASV, your inhale and exhale pressures can be set the same--i.e., no Bipap--and the ASV function will still deliver puffs of air to "nudge" you to breath, when necessary. With the Resmed ASV, inhale and exhale have to be a minimum of 3cm apart.

For both ASV machines, when ASV kicks in, it delivers puffs of air at successively higher pressures until by the third puff, it's at the maximum pressure support (max PS) set.

[jamiswolf]

Moresleep wrote: For both ASV machines, when ASV kicks in, it delivers puffs of air at successively higher pressures until by the third puff, it's at the maximum pressure support (max PS) set.

OK, bear with me because I have some misunderstanding here. I thought PS was the difference between ipap and epap. Or is that a difference in definitions between regular Bipaps and the ASV units.

Here's how you could explain this: What do you actually adjust on the machine to determine the maximum pressure support? Is there a max PS setting where you put in 25 or 30 (whatever is needed)?

Thanks for your patience and I appreciate the help. Believe me, I've read all the threads I could find and I seem to be getting more confused.
Cheers,
Jamis

[moresleep]

Now you've got me confused. Let's see; on my legacy Respironics ASV, you have:

Max Pressure
Min EPAP
Max EPAP
Min Pressure Support (PS)
Max Pressure Support

Min PS is the difference between Epap and Ipap. But, if Min PS=0, there is no difference and the machine is not in Bipap mode. But, thinking about it, it might be more accurate to say the machine does not start in Bipap mode when Min PS=0, since to some extent the machine can act as an Auto Bipap, and I am not sure that setting Min PS=0 keeps Ipap (i.e. PS) from ranging.

The Max Pressure Support setting, so long as it's below Max Pressure, determines the max pressure the ASV function can use when it kicks in to try to get the user to take a breath; otherwise Max Pressure determines that max pressure.

[moresleep]

Thanks for trying, John. But what will it do for me? Right now I'm still having the same old issues of the machine switching to inhalation while I'm still exhaling. BPM is set at 6. Rise time is at the max of 6. Ti is set at 1. So, am I correct in thinking that if I move the Ti up to 3 it might help? One of these days I have to find a doctor who is familiar with these things.....

T1=1 strikes me as way too low for anyone who is not a youngster. I have Ti=2.7 on my machine. I found that anything less was just not giving me enough time to complete my breath.

[ameriken]

These machines are amazing but trying to understand each function, especially how it relates to other functions as well as how it all improves our nighttime breathing is god-awfully difficult.

[ameriken]

... Rise time and Flex. ...

That's a good question. The answers I am providing are "As I Understand Them". I might be wrong. But I think this is all correct.

First, I do know that "Flex" is a technology first developed by Respironics to address the discomfort of sleeping against a continuous pressure provided by CPAP units. This technology/technique drops the pressuring during the expiration phase of breathing. It is NOT Bi-Level PAP therapy (BiPAP), which has a prescribed pressure for both inhalation and exhalation. Rather, it drops the pressure during exhalation to make it easier to breathe. As I've noted before, this drop does not "support" breathing. The pressure will not be enough to maintain an open airway.

Respironics then went on to create different Flex technologies for different types of units. For example, there is a Flex technology for BiPAP units. But they basically work on the same principle - decreasing the pressure a little during exhalation to make it easier to breathe.

Second, the "Rise Time" value on the ASV unit shows the ventilator background of the ASV units. Rise time determines the speed with which the flow or pressure of the ventilator rises from exhalation to inhalation. The time it takes for this switch from one to the other is the "Rise Time".

... Can someone explain what they are and what they are supposed to do, ...

See above.

... what is the difference between rise time and flex, ...

See above.

... and what is the difference between a rise time of 1 and a rise time of 6, ...

A rise time of one (1) is a VERY short rise from exhalation to inhalation. Most people would find that to be COMPLETELY unacceptable. To me (when I've tinkered with it) it feels as if I was suddenly having some shop pressure tool pumping me full of air. No thanks!

A rise time of six (6) is much longer time to rise from exhalation to inhalation. Most people may find that to be too long. In fact, it might actually limit the amount of air that you inhale. If it is too long and you the unit decides you have not cycled your breathing it might actually truncate the intake and switch you to exhalation pressure. Also not good. To compensate, a long rise time may require a higher pressure from the ASV to meet your needs.

So, you might try to see if a Rise Time of 5 or 4 would help reduce the high pressures, by moving you more quickly to the inhalation pressure. But don't overdo it by moving to a Rise Time of 2 or 3. You would feel very rushed in that case.

... and the difference between a 1 and 3 in flex? ...

The 1 to 3 denotes the drop off in pressure during the expiration phase of breathing. The least decrease in pressure is at a setting of 1. The greatest decrease in pressure is at a setting of 3.

... Can these settings impact therapy and AHI? ...

Absolutely, see the last graph in the following summary of a couple studies. At 3 the pressure decreases to the point that the number of obstructive sleep apnea events increase. The more you back off the pressure, the more it is likely the pressure will not be enough to avoid an obstructive apnea.

http://cflex.respironics.com/PDF/101663 ... tudies.pdf

Interestingly, due to the decreased pressure the studies confirm my own experience. I got better sleep with a C-Flex setting of 1.

As to the Rise Time setting, as you can see a slightly lower Rise Time might decrease the top pressure to help you attain normal respiration during a central apnea.

Hope that helps.

John, I just wanted to say thanks for your help above.Turns out the flex setting was screwing with my AHI. After I turned the flex off, and set the rise time to 4, my AHI's have dropped. I did have one night at 16, but otherwise it looks like it has dropped into the 5 to 10 range.